Identifying a vortex in an electro-anatomical map

ABSTRACT

A system for identifying vortices in a vector map including multiple vectors, the system includes a processor and an output device. The processor is configured to: (i) define one or more closed loops on the vector map, and (ii) for each closed loop, identify a plurality of the vectors that cross the closed loop, calculate a vector sum of the identified vectors, and decide based on the vector sum whether a vortex is located inside the closed loop. The output device is configured to indicate one or more identified vortices to a user.

FIELD OF THE INVENTION

The present invention relates generally to medical devices, and moreparticularly to methods and systems for identifying a vortex in anelectro-anatomical map.

BACKGROUND OF THE INVENTION

Various techniques for identifying arrhythmias in electro-anatomicalmaps have been published.

For example, U.S. Patent Application Publication No. 2019/0104958describes methods and systems for determination and mapping of vectorfields which characterize wavefront motion through space and time. Theinventive methods and systems utilize data from spatially distributedlocations and maps wavefront vector flow fields in an entirely automatedmanner. These maps can be used to characterize the activation as planar,centrifugal, or rotational. Further, the strength of rotation ordivergence is determined from these fields and can be used to selectspatial points of significantly increased rotational or focal activity.As applied to electrophysiological data recorded during heart rhythmdisorders in patients, the inventive method provides a means of visualinterpretation of complex activation maps. The information related tothe strength and location of rotation and centrifugal activity duringepisodes of arrhythmia can guide therapies designed to treat suchdisorders.

U.S. Patent Application Publication No. 2020/0375489 describes a methodincluding receiving, in a processor, a two-dimensional (2D)electroanatomical (EA) map of an interior surface of at least a portionof a cavity of an organ of a patient, the 2D EA map includingelectrophysiological (EP) values measured at respective locations on theinterior surface. A complex analytic function is fitted to a set of theEP values that were measured in a given region of the 2D EA map. Asingularity is identified in the fitted complex analytic function. Theregion is projected onto a three-dimensional (3D) EA map of the interiorsurface. At least part of the 3D EA map is presented to a user,including indicating an arrhythmogenic EP activity at a location on the3D EA map corresponding to the singularity identified in the fittedcomplex analytic function.

SUMMARY OF THE INVENTION

An embodiment of the present invention that is described herein providesa system for identifying vortices in a vector map including multiplevectors, the system includes a processor and an output device. Theprocessor is configured to: (i) define one or more closed loops on thevector map, and (ii) for each closed loop, identify a plurality of thevectors that cross the closed loop, calculate a vector sum of theidentified vectors, and decide based on the vector sum whether a vortexis located inside the closed loop. The output device is configured toindicate one or more identified vortices to a user.

In some embodiments, at least one of the closed loops includes a circle.In other embodiments, the processor is configured to decide that thevortex is located inside the closed loop in response to the vector sumbeing less than a threshold. In yet other embodiments, the processor isconfigured to adjust one or both of a size and a shape of at least oneof the closed loops, so as to identify the vortex.

In an embodiment, the processor is configured to adjust a position of atleast one of the closed loops, so as to identify the vortex. In anotherembodiment, the vector map includes an electro-anatomical (EA) map of apatient heart, the multiple vectors are indicative of electrical signalspropagating over a surface of the patient heart, and by identifying thevortex, the processor is configured to identify one or more re-entrantarrhythmias in the patient heart.

There is additionally provided, in accordance with an embodiment of thepresent invention, a method for identifying vortices in a vector mapincluding multiple vectors, the method includes defining one or moreclosed loops on the vector map, and for each closed loop, identifying aplurality of the vectors that cross the closed loop. A vector sum of theidentified vectors is calculated, and based on the vector sum, decidingwhether a vortex is located inside the closed loop. One or moreidentified vortices are indicated to a user.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof, taken together with thedrawings in which:

FIG. 1 is a schematic, pictorial illustration of a catheter-basedtracking and ablation system, in accordance with an exemplary embodimentof the present invention;

FIG. 2 is a schematic, pictorial illustration of a three-dimensional(3D) electro-anatomical (EA) map having wave vectors, in accordance withan exemplary embodiment of the present invention; and

FIG. 3 is a flow chart that schematically illustrate a method foridentifying vortices in a vector map comprising multiple wave vectors,in accordance with exemplary embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

Re-entrant arrhythmias occur in a patient heart when an electricalimpulse recurrently travels in a tight circle within the heart, ratherthan moving from one end of the heart to the other end, and thenstopping. When conducting electro-anatomical (EA) mapping of at least aportion of the patient heart, at least some re-entrant arrhythmias mayappear as vortices of wave vectors produced during the EA mapping. Whena vortex occurs in the patient heart, the directions of the wave vectorsare typically distributed symmetrically and therefore, the wave vectorsassociated with the vortex are mutually canceled.

In principle, an experienced cardiac electrophysiologist, also referredto herein as a physician, may identify one or more vortices by visuallyinspecting the arrangement of wave vectors presented on an EA map.However, an increasing number of data points and wave vectors presentedover EA maps, may conceal from the physician, one or more vortices.Moreover, a qualitative identification of a vortex (using a visualassessment) may result in, for example, a different assessment of thesame anatomical phenomena, among different physicians. Therefore, it isimportant to develop a quantitative criterion for identifying a vortexin an EA map.

Embodiments of the present invention that are described hereinbelowprovide improved techniques for identifying vortices based on wavevectors of a vector map presented over an EA map of a patient heart. Inthe context of the present disclosure and in the claims, the terms“vector” and “wave vector” are used interchangeably and refer to displayobjects indicative of electrical signals propagating over a surface ofthe patient heart.

In some embodiments, the EA map comprises various types of displayobjects, such as but not limited to wave vectors of a vector map, whichare presented over an anatomical map of the patient heart.

In some embodiments, a system, which comprises a processor and an outputdevice, is configured to identify vortices in the vector map having theplurality of wave vectors.

In some embodiments, the processor is configured to define one or moreclosed loops on the vector map, the closed loops may have a shape of acircle or any other suitable shape. When a vortex appears within theclosed loop, the directions of the wave vectors that cross the closedloop shape are expected to be distributed symmetrically around theclosed loop and therefore will cancel each other out when summed.

In some embodiments, for each closed loop, the processor is configuredto identify a plurality of the vectors that cross the closed loop. Theprocessor is further configured to calculate a vector sum of theidentified vectors, and to decide based on the vector sum, whether avortex is located inside the closed loop.

In some embodiments, the processor is configured to hold a threshold,and to compare between the vector sum and the threshold. Based on thecomparison, the processor is configured to decide that a vortex islocated inside the closed loop when the vector sum is smaller than thethreshold.

In some embodiments, the processor is configured to adjust at least oneof the size, the shape, and the position of the closed loop, so as toidentify one or more vortices in the vector map presented over the EAmap. The processor is further configured to produce an output indicativeof the one or more identified vortices, and the position of eachidentified vortex.

In some embodiments, the output device, e.g., a display, is configuredto present the output produced by the processor on the EA map, using anysuitable display objects. As described above, the wave vectors of thevector map are indicative of electrical signals propagating over asurface of the patient heart. Thus, by identifying the vortex, theprocessor is configured to identify one or more re-entrant arrhythmiasthat occurred in the patient heart.

The disclosed techniques provide cardiac electrophysiologists withidentification and mapping of vortices in electro-anatomical (EA) mapsof patient heart. The identification is based on a quantitative analysisof selected sections of the heart, which are suspected of havingre-entrant arrhythmias. Moreover, as opposed to the cardiacelectrophysiologist, who may err in identifying a vortex due to acongestion of information displayed over the EA map, the disclosedtechniques improve the identification accuracy of cardiac vortices, inresponse to an increase in the amount of electrophysiologicalmeasurements presented over the EA map of the heart.

System Description

FIG. 1 is a schematic, pictorial illustration of a catheter-basedtracking and ablation system 20, in accordance with an exemplaryembodiment of the present invention.

In some embodiments, system 20 comprises a catheter 22, in the presentexample a cardiac catheter, and a control console 24. In the embodimentdescribed herein, catheter 22 may be used for any suitable therapeuticand/or diagnostic purposes, such as sensing electro-anatomical signalsand/or ablation of tissue in a heart 26 of a patient 28.

In some embodiments, console 24 comprises a processor 34, typically ageneral-purpose computer, with suitable front end and interface circuitsfor receiving signals via catheter 22 and for controlling the othercomponents of system 20 described herein. Console 24 further comprises auser display 35, which is configured to receive from processor 34 a map27 of heart 26, and to display map 27. In some embodiments, map 27 maycomprise any suitable type of three-dimensional (3D) anatomical mapproduced using any suitable technique. For example, the anatomical mapmay be produced using an anatomical image produced by using a suitablemedical imaging system, or using a fast anatomical mapping (FAM)techniques available in the CARTO™ system, produced by Biosense WebsterInc. (Irvine, Calif.), or using any other suitable technique, or usingany suitable combination of the above.

Reference is now made to an inset 23. In some embodiments, prior toperforming an ablation procedure, a physician 30 inserts catheter 22through the vasculature system of a patient 28 lying on a table 29, soas to perform electro-anatomical (EA) mapping of tissue in question ofheart 26.

In some embodiments, catheter 22 comprises a distal-end assembly 40having multiple sensing electrodes (not shown). For example, distal-endassembly 40 may comprise:

(i) a basket catheter having multiple splines, each spline havingmultiple sensing electrodes, (ii) a balloon catheter having multiplesensing electrodes disposed on the surface of the balloon, or (iii) afocal catheter having multiple sensing electrodes. Each sensingelectrode is configured to produce, in response to sensingelectrophysiological (EP) signals in tissue of heart 26, one or moresignals indicative of the sensed EP signals.

In some embodiments, the proximal end of catheter 22 is connected, interalia, to interface circuits (not shown), so as to transfer these signalsto processor 34 for performing the EA mapping. In some embodiments,during the EA mapping, the signals produced by the sensing electrodes ofdistal-end assembly 40 may comprise thousands of data points, e.g.,about 50,000 data points or even more, which may be stored in a memory38 of console 24. Based on the data points, processor 34 is configuredto present on map 27, wave vectors, also referred to herein as vectors(shown in FIG. 2 below), which are indicative of electrical signalspropagating over the surface of heart 26.

In some embodiments, based on the presented vectors, physician 30 and/orprocessor 34, may identify one or more types of arrhythmias thatoccurred in heart 26. Moreover, physician 30 may determine one or moresites for treating the arrhythmias, e.g., by ablating tissue in heart26.

However, physician 30 may have difficulties to review and analyze theaforementioned large number of data points and vectors, which mayprolong the duration of the ablation procedure. Moreover, the largeamount of data points and vectors may confuse physician 30, andtherefore, may reduce the quality of the EA analysis and correspondingtreatment, e.g., tissue ablation.

In the context of the present disclosure and in the claims, the terms“about” or “approximately” for any numerical values or ranges indicate asuitable dimensional tolerance that allows the part or collection ofcomponents to function for its intended purpose as described herein.

In some cases, heart 26 may have one or more sites of re-entrantarrhythmias, also referred to herein as “re-entry.” In some embodiments,processor 34 is configured to identify, in an EA map (e.g., map 27) ofheart 26, multiple vectors arranged in a shape, which is indicative of are-entry. Techniques for identifying re-entrant arrhythmias aredescribed in detail in FIGS. 2 and 3 below.

In other embodiments, catheter 22 may comprise one or more ablationelectrodes (not shown) coupled to distal-end assembly 40. The ablationelectrodes are configured to ablate tissue at a target location of heart26, which is determined based on the analysis of the EA mapping of thetissue in question of heart 26. After determining the ablation plan,physician 30 navigates distal-end assembly 40 in close proximity to thetarget location in heart 26 e.g., using a manipulator 32 formanipulating catheter 22. Subsequently, physician 30 places one or moreof the ablation electrodes in contact with the target tissue, andapplies, to the tissue, one or more ablation signals. Additionally oralternatively, physician 30 may use any different sort of suitablecatheter for ablating tissue of heart 26 so as to carry out theaforementioned ablation plan.

In some embodiments, the position of distal-end assembly 40 in the heartcavity is measured using a position sensor (not shown) of a magneticposition tracking system. In the present example, console 24 comprises adriver circuit 41, which is configured to drive magnetic fieldgenerators 36 placed at known positions external to patient 28 lying ontable 29, e.g., below the patient's torso. The position sensor iscoupled to the distal end, and is configured to generate positionsignals in response to sensed external magnetic fields from fieldgenerators 36. The position signals are indicative of the position thedistal end of catheter 22 in the coordinate system of the positiontracking system.

This method of position sensing is implemented in various medicalapplications, for example, in the CARTO™ system, produced by BiosenseWebster Inc. (Irvine, Calif.) and is described in detail in U.S. Pat.Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and6,332,089, in PCT Patent Publication WO 96/05768, and in U.S. PatentApplication Publication Nos. 2002/0065455 A1, 2003/0120150 A1 and2004/0068178 A1, whose disclosures are all incorporated herein byreference.

In some embodiments, the coordinate system of the position trackingsystem are registered with the coordinate systems of system 20 and map27, so that processor 34 is configured to display, the position ofdistal-end assembly 40, over the anatomical or EA map (e.g., map 27).

In some embodiments, processor 34, typically comprises a general-purposecomputer, which is programmed in software to carry out the functionsdescribed herein. The software may be downloaded to the computer inelectronic form, over a network, for example, or it may, alternativelyor additionally, be provided and/or stored on non-transitory tangiblemedia, such as magnetic, optical, or electronic memory.

This particular configuration of system 20 is shown by way of example,in order to illustrate certain problems that are addressed byembodiments of the present invention and to demonstrate the applicationof these embodiments in enhancing the performance of such a system.Embodiments of the present invention, however, are by no means limitedto this specific sort of example system, and the principles describedherein may similarly be applied to other sorts of medical systems.

Automatically Identifying Vortices Indicative of Re-Entrant Arrhythmias

FIG. 2 is a schematic, pictorial illustration of a three-dimensional(3D) electro-anatomical (EA) map 50, in accordance with an exemplaryembodiment of the present invention. EA map 50, comprises a 3Danatomical map of at least a portion of heart 26, and has, inter alia,multiple vectors 55 indicative of electrical signals propagating overthe surface of heart 26. EA Map 50, which is also referred to herein asa map 50, for brevity, may replace for example, map 27 of FIG. 1 above.

In some cases, heart 26 may have re-entrant, or other sorts ofarrhythmias. Re-entrant arrhythmias typically occur when an electricalimpulse recurrently travels in a closed loop, typically in a tightcircle within heart 26, rather than moving from one end of the heart tothe other end, and then stopping. As a sort of re-entry, vortices ofexcitation in the myocardium of heart 26, are considered to be amechanism of life-threatening cardiac arrhythmias. In principle,physician 30 may identify one or more vortices by visually inspectingthe arrangement of wave vectors 55 presented over EA map 50. However,the increased number of data points and wave vectors 55 in the EA maps(e.g., EA maps 27 and 50 of FIGS. 1 and 2 , respectively), may concealone or more vortices from physician 30. Moreover, a qualitativeidentification of a vortex (using a visual inspection) may result in,for example, a different assessment of the same anatomical phenomena,among different physicians. Therefore, it is important to develop aquantitative criterion for identifying vortices in EA map 50.

In some embodiments, processor 34 is configured to define one or moreclosed loops, in the present example, circles 52 and 54, on EA map 50.As described above, EA map 50 comprises a vector map having multiplevectors 55. In some embodiments, circles 52 and 54 may be defined withina section of heart 26, which is selected by physician 30 on EA map 50.Additionally or alternatively, processor 34 is configured to scan atleast a portion of EA map 50, and based on the arrangement of vectors 55in the scanned area(s), processor 34 may define the position, the size,the shape, and the amount of the closed loops defined and placed over EAmap 50.

Reference is now made to insets 62 and 64 showing circles 52 and 54,respectively. In some embodiments, circle 52 is defined on EA map 50such that multiple vectors 55A, from among vectors 55, cross theperimeter of circle 52. Similarly, circle 54 is defined on EA map 50,such that multiple vectors 55B, from among vectors 55, cross theperimeter of circle 54.

In some embodiments, processor 34 is configured to identify vectors 55Aand 55B that cross circles 52 and 54, respectively. Moreover, processor34 is configured to calculate, for each of the aforementioned circles, avector sum of the identified vectors, and to decide, based on the vectorsum, whether a vortex is located inside the respective circle.

In some embodiments, processor 34 may hold a threshold, which may bepredefined by physician 30 as a percentage of a normalized range ofvectors 55A and 55B that cross circles 52 and 54 (e.g., smaller thanabout 10% of the normalized range) that defines whether or not thevector sum is indicative of a vortex within the circle, or within anyother shape of a closed loop defined by the processor (e.g., anellipse).

In such embodiments, processor 34 is configured to compare between thevector sum and the threshold, and in case the vector sum is smaller thanthe threshold, processor 34 identifies a vortex within the respectiveclose loop.

Reference is now made again to inset 62. When a vortex occurs in heart26, the directions of vectors 55A are typically distributedsymmetrically and therefore, vectors 55A are mutually canceled. In theexample of circle 52, the magnitude of the vector sum of vectors 55A isabout zero, which is smaller than the threshold. In some embodiments,based on the vector sum and the threshold, processor 34 is configured todecide that a vortex is located inside circle

In some embodiments, processor 34 is configured to produce an outputindicating that the vortex is identified inside circle 52. Moreover,display 35 or any other suitable output device, may display theidentified vortex to physician 30, e.g., at the original position ofcircle 52 on EA map 50.

Reference is now made back to inset 64. In the example of circle 54, avector 65 shows a calculated vector sum of vectors 55B having adirection and magnitude. In the present example, the magnitude of vector65 is larger than about 10 percent of the normalized range of vectors55B, which is larger than the threshold. Therefore, based on the vectorsum and the threshold, processor 34 is configured to decide that novortex is located inside circle 54. Moreover, processor 34 is configuredto output, to display 35 or to any other suitable output device, anindication that the vector sum of wave vectors 55B is propagating acrossheart 26 in the direction of vector 65.

In other embodiments, in addition to or instead of circles 52 and 54,processor 34 is configured to define on EA map 50, other sorts of closedloops having any suitable shape and/or size. Moreover, processor 34 isconfigured to adjust the size and/or the shape of one or more of theclosed loops, so as to identify one or more vortices in EA map 50.

In other embodiments, processor 34 is configured to adjust the positionof a closed loop (e.g., circle 54) on EA map 50, so as to identify avortex at the adjusted position of circle 54 on EA map 50. Moreover,processor 34 is configured to adjust any combination of size, shape, andposition of one or more of the closed loops, in order to check whetheror not EA map 50 has additional vortices.

In some embodiments, display 35 (or any other suitable type of outputdevice) is configured to indicate one or more identified vortices tophysician 30 (or to any other user of system 20), using any suitabletechnique. For example, a pop-up displayed at the position of theidentified vortex, a color applied to the closed loop (e.g., circle 52)that is indicative of an identified vortex, a list with positions andproperties of the identified vortices, or any other suitable type ofindication.

In some embodiments, based on the presence of one or more vorticesidentified by processor 34, physician 30 can: (i) decide whether or notheart 26 has one or more re-entrant arrhythmias, and (ii) based on theposition of each re-entrant arrhythmias, physician 30 may determine atreatment, such as but not limited to target location(s), and parametersof radiofrequency (RF) ablation, in tissue of heart 26.

In other embodiments, processor 34 is configured to: (i) define multipleelements at different positions on EA 50, (ii) identify vectors, withinan area surrounded by the multiple elements, or along a perimetersurrounding the multiple elements, and (iii) calculate a vector sum ofthe vectors, so as to decide (based on the vector sum), whether a vortexis located inside the area surrounded by three or more of the multipleelements.

FIG. 3 is a flow chart that schematically illustrates a method foridentifying vortices in EA map 50 having multiple vectors 55, 55A and55B, in accordance with exemplary embodiments of the present invention.

The method begins at a circles definition step 100, with processor 34(i) receiving EA map 50 having multiple vectors 55, 55A and 55B, and(ii) defining on EA map 50, one or more closed loops, such as but notlimited to circles 52 and 54, as described in detail in FIG. 2 above.

At a vortex identification step 102, for each of the defined circles,processor 34 (i) identifies a plurality of the vectors that cross aperimeter of the circle, (ii) calculates a vector sum of the identifiedvectors, and (iii) decides, based on the vector sum, whether a vortex islocated inside the circle. In some embodiments, processor 34 holds athreshold and compares between the vector sum and the threshold, inorder to decide whether a vortex is located inside the circle, asdescribed in detail in FIG. 2 above. In the example of circle 52, thevector sum is smaller than the threshold, so that a vortex is identifiedwithin circle 52. In the example of circle 54, the vector sum is largerthan the threshold, so that no vortex is identified within circle 54.

At a presentation step 104 that concludes the method, processor 34presents to physician 30 (e.g., on display 35), an output indicative ofone or more vortices identified in EA map 50. Several embodimentsrelated to the presentation of the vortices are described in detail FIG.2 above.

In some embodiments, EA map 50 comprises a 3D anatomical map of at leasta portion of heart 26, and vectors 55, 55A and 55B comprise wave vectorsindicative of electrical signals propagating over the surface of heart26, as described in FIG. 2 above. In some embodiments, processor 34 isconfigured to adjust one or both of the size and the shape of at leastone of the closed loops (e.g., circles 52 and 54), so as to identify thevortex. Moreover, processor 34 is configured to adjust the position ofat least one of the closed loops (e.g., circle 54), so as to identify anadditional vortex. As described in detail in FIG. 2 , based on theidentification of the one or more vortices, processor is configured toidentify one or more re-entrant arrhythmias in heart of patient 28. Inresponse to identifying the one or more re-entrant arrhythmias,physician 30 may determine a treatment, such as but not limited to an RFablation of the heart tissue, for treating the re-entrant arrhythmias.

Although the embodiments described herein mainly address identificationof one or more vortices indicative of re-entrant arrhythmias in thepatient heart, the methods and systems described herein can also be usedin other cardiac applications.

It will thus be appreciated that the embodiments described above arecited by way of example, and that the present invention is not limitedto what has been particularly shown and described hereinabove. Rather,the scope of the present invention includes both combinations andsub-combinations of the various features described hereinabove, as wellas variations and modifications thereof which would occur to personsskilled in the art upon reading the foregoing description and which arenot disclosed in the prior art. Documents incorporated by reference inthe present patent application are to be considered an integral part ofthe application except that to the extent any terms are defined in theseincorporated documents in a manner that conflicts with the definitionsmade explicitly or implicitly in the present specification, only thedefinitions in the present specification should be considered.

1. A system for identifying vortices in a vector map comprising multiplevectors, the system comprising: a processor, which is configured to:define one or more closed loops on the vector map; and for each closedloop, identify a plurality of the vectors that cross the closed loop,calculate a vector sum of the identified vectors, and decide based onthe vector sum whether a vortex is located inside the closed loop; andan output device, which is configured to indicate one or more identifiedvortices to a user.
 2. The system according to claim 1, wherein at leastone of the closed loops comprises a circle.
 3. The system according toclaim 1, wherein the processor is configured to decide that the vortexis located inside the closed loop in response to the vector sum beingless than a threshold.
 4. The system according to claim 1, wherein theprocessor is configured to adjust one or both of a size and a shape ofat least one of the closed loops, so as to identify the vortex.
 5. Thesystem according to claim 1, wherein the processor is configured toadjust a position of at least one of the closed loops, so as to identifythe vortex.
 6. The system according to claim 1, wherein the vector mapcomprises an electro-anatomical (EA) map of a patient heart, wherein themultiple vectors are indicative of electrical signals propagating over asurface of the patient heart, and wherein, by identifying the vortex,the processor is configured to identify one or more re-entrantarrhythmias in the patient heart.
 7. A method for identifying vorticesin a vector map comprising multiple vectors, the method comprising:defining one or more closed loops on the vector map, and for each closedloop, identifying a plurality of the vectors that cross the closed loop;calculating a vector sum of the identified vectors, and deciding basedon the vector sum whether a vortex is located inside the closed loop;and indicating one or more identified vortices to a user.
 8. The methodaccording to claim 7, wherein defining the closed loops comprisesdefining at least a circle among the closed loops.
 9. The methodaccording to claim 7, wherein deciding based on the vector sum comprisesdeciding that the vortex is located inside the closed loop in responseto the vector sum being less than a threshold.
 10. The method accordingto claim 7, and comprising adjusting one or both of a size and a shapeof at least one of the closed loops, so as to identify the vortex. 11.The method according to claim 7, and comprising adjusting a position ofat least one of the closed loops, so as to identify the vortex.
 12. Themethod according to claim 7, wherein the vector map comprises anelectro-anatomical (EA) map of a patient heart, wherein the multiplevectors are indicative of electrical signals propagating over a surfaceof the patient heart, and wherein, identifying the vortex comprisesidentifying one or more re-entrant arrhythmias in the patient heart.